1. Field of Invention
The present invention relates to air-fuel ratio control apparatus of internal combustion engine.
2. Description of Related Art
For purifying exhaust gas from the internal combustion engine, an exhaust purifying catalyst (three-way catalyst) is placed on the exhaust path, an air-fuel ratio sensor is located on the exhaust path to detect the air-fuel ratio (A/F), and feedback control is implemented so as to control an air-fuel mixture toward the stoichiometric air-fuel ratio, thereby simultaneously decreasing nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC). The purification efficiency of exhaust gas emitted from the internal combustion engine is further increased effectively by carrying out the foregoing feedback control with accuracy.